Lecture 14: membrane structure and function Flashcards
structure of micelle
spherical shell of lipids with single FA tail
critical micellar concentration [CMC]
concentration of lipid when addition of more monomers to solution doesn’t increase the monomer concentration
micelle formation entropically driven by ____
hydrophobic effect; hydrocarbon tails driven towards each other to form micelles
what determines CMC value for different lipids?
chemical composition of lipid
structure of triacylglycerols
- glycerol backbone + 3 fatty acids [ester linkages]
- nonpolar NOT AMPHIPATHIC
- NO POLAR HEAD GROUP = NO CMC = CANT FORM MICELLES
polar head groups of triacylglycerols
NO POLAR HEAD GROUP
role of pancreatic lipase
cleaves fatty acid tails from glycerol backbone = produces free fatty acid chains that can go on to form their own micelles [now amphipathic because no longer attached to triacylglycerol]
transition of triacylglycerols to free fatty acid chain requires (2)
- formation of bile salt micelles
- activity of pancreatic lipase
each hydrocarbon tail is a source of energy but ___
but needs to be cleaved off glycerol backbone
structure of lipid bilayer in gel phase
- head groups tightly packed
- regular tails
- thicker membrane
structure of lipid bilayer in liquid crystal phase
- head groups loosely packed
- tails disordered = more movement
- thinner membrane
Tm
temp required to transition from gel into liquid crystal; midpoint of melting curve
lower Tm vs higher Tm
- lower Tm = more fluid membrane
- higher Tm = less fluid membrane
why does Tm dec with inc head size?
smaller heads mean tails can be closer to each other = more VDW interactions so bigger heads means less interactions = increased fluidity
why does Tm inc with inc fatty acid tail length?
inc # of VDW interactions = more energy required to reach a fluid state; more C on tail = less fluid
